Biomass Yield, Bioenergy Trait Characteristics, and Cell-Wall Composition of Dryland Sweet Pearl Millet Grown At Multiple Locations in Colorado.

Biofuels are a promising source of energy in place of petroleum, however current bioenergy crops require excessive inputs. A sustainable bioenergy industry will require drought tolerant, high-residue crops that are well adapted to semi-arid areas and can act as feedstocks for bioenergy production. Sweet pearl millet (Pennisetum glaucum) was grown at four locations in Northern Colorado under dryland conditions to identify how the environment can impact bioenergy traits. A number of biomass traits were assessed including plant size and architecture, sap brix, cell-wall composition and physiological traits of leaf gas exchange. Total biomass yields ranged from 11.5 Mg ha-1 to 15.1 Mg ha-1 with total available water that ranging from 56 to 96 mm. Cell-wall cellulose, hemicellulose and lignin content were higher in stems than in leaves. Nearly all measured traits were impacted by the environment including sap brix, plant height, leaf number, cell-wall composition, tissue partitioning (stems, leaves, grain) and total biomass yields. We investigated available growing degree-days, rainfall and total available solar radiation as environmental parameters that may affect bioenergy phenotypes. Several traits were positively correlated to all parameters including plant height and stem and grain tissue partitioning. Leaf tissue partitioning was negatively correlated to the environment parameters. Growing degree-days positively influenced stem diameter, leaf number and the individual internode lengths. Total biomass and sap brix measurements were positively correlated while increased leaf number negatively impacted stem sugar accumulation. This study showed that a drought tolerant crop such as sweet pearl millet can produce quality biomass under water-limiting growing conditions. Future work includes expanding this study to three locations, with 20 drought tolerant plant entries (sorghum and millet), with rainfed and irrigated treatments.